This application claims the benefit of Japanese Patent Application Nos. 2000-124191 filed Apr. 25, 2000 and 2001-28286 filed on Feb. 5, 2001 in the Japanese Patent Office, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to the physical format of a rewritable optical disc using a phase change medium or a magneto-optical (MO) medium, or a write once type optical disc using a pigment based medium, and more particularly, to the physical format suitable for handling data in a large amount such as image data or voice data.
2. Description of the Related Art
As a large capacity storage medium for a computer, a DVD (digital versatile disc), an MO disc (magneto-optical disc), or a CD (compact disc) is commercially used. Also, due to the spread of computers, a need for editing data stored in a storage medium increases so that a storage medium in which data can be modified or added is required.
As a rewritable storage medium on which a user can write and erase data many times, there is a DVD-RAM (DVD-random access memory) using a phase change medium, an MO disc using an MO medium, and a CD-RW (CD-rewritable). Also, as a write once type storage medium on which a user can write data only one time, there is a CD-R (CD-recordable) using a pigment based medium. In these storage media, addresses for identifying the positions where data is written are stored in advance. Also, an ID (identification) portion for indicating addresses is provided on the DVD-RAM or MO disc, separate from a portion where user data is stored.
Also, in the CD-RW or CD-R, the addresses are managed by a wobble/address method using an FM (frequency modulation) modulation. Here, the wobble means a wave and tracks on a disc are formed to be waved in a radial direction of the disc. That is, in the CD-RW or CD-R, the addresses are stored by changing the frequency of a wobble (wave) of a track. Thus, in the CD-RW or CD-R, the user data and address are stored along the track by being overlapped.
The above conventional technology has the following problems.
That is, in the DVD-RAM or MO disc, since the ID portion is needed separately from the portion where user data is stored, the efficiency in use of the area of a disc surface is deteriorated. Also, since the structures of the disc surfaces of the portion where user data is stored and the ID portion are different from each other, a process for manufacturing this disc is complicated so that manufacturing a disc is difficult. In particular, in the DVD-RAM, since the ID portion is arranged to be zigzag, a manufacturing process becomes more difficult.
Also, in the CD-RW or CD-R, since the address corresponds to the frequency of the wobble, in order for a disc reading apparatus to read the address, there is a need for reading a signal (wobble) of a different frequency, which makes the structure of the disc reading apparatus complicated.
Also, since the frequency of a wobble of a track is changed according to the value of an address, the length of a track needed for storing the address differs according to the value of the address. Thus, control of writing data is complicated.
Also, since the above method of matching the address to the frequency of the wobble is a method of storing the address by modulating the wobble by an FM modulation, the required C/N (carrier to noise) ratio is great so that it is difficult to secure reliability in reading and writing.
Also, a complicated demodulation circuit is needed to demodulate second sub-information from an optical disc where first and the second sub-information are recorded.
FIG. 13 is a block diagram showing the structure of a demodulation circuit for demodulating the second sub-information according to the conventional technology. Referring to the drawing, a wobble signal which is an input signal to the demodulation circuit is input to a multiplier 12 via a band-pass filter 11. A signal from a local oscillator 13 is input to the multiplier 12. An output signal of the multiplier 12 passes a low-pass filter 14 and is input to a plus/minus determining portion 15. The result of demodulation is output from the plus/minus determining portion 15.
That is, since detection of synchronism is needed in the conventional technology, the local oscillator 13 for outputting a signal of which the frequency and phase are synchronized with those of a wobble signal which is an input signal to the demodulation circuit, is needed to be provided in the demodulation circuit, which makes the demodulation circuit complicated.
To solve the above problems, it is an object of the present invention to provide an optical disc which has a superior efficiency in use of the area of a disc surface, of which manufacturing is made easy, by which the structure of a disc reading apparatus is simplified, which simplifies control of writing data on a disc, in which the C/N ratio is low, and in which reliability in reading and writing is high.
Also, it is an object of the present invention to provide an optical disc which simplifies the structure of the demodulation circuit.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, there is provided an optical disc has a track for recording user data, the optical disc comprising a wobble portion waved in a radial direction of the optical disc and a non-wobble portion that is not waved provided on the track, first sub-information and second sub-information which are data other than the user data recorded on the track by being overlapped, by using a combination of the wobble portion and the non-wobble portion, in the first sub-information, the length of at least one of the wobble portion and the non-wobble portion is different when a bit takes a logical value xe2x80x9c0xe2x80x9d and when the bit takes a logical value xe2x80x9c1xe2x80x9d, and in the second sub-information, a phase of a wave in the wobble portion when a bit takes a logical value xe2x80x9c0xe2x80x9d is different from a phase of a wave in the wobble portion when the bit takes a logical value xe2x80x9c1xe2x80x9d.
It may be in the present invention that, in the first sub-information, when a bit takes one of logical values xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, the non-wobble portion exists, and when the bit takes the other of logical values xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, the non-wobble portion does not exist.
It may be in the present invention that the length of the non-wobble portion is an integer multiple of one period of a wave in the wobble portion.
It is preferred in the present invention that the first sub-information is converted sub-information which is converted from original sub-information according to a predetermined rule of conversion.
It may be in the present invention that the lengths of the wobble portion and the non-wobble portion are integer multiples of one period of a wave in the wobble portion.
It may be in the present invention that, in the second sub-information, a phase of a wave of the wobble portion at transition points from the wobble portion to the non-wobble portion and from the non-wobble portion to the wobble portion, is a predetermined phase.
It may be in the present invention that, in the second sub-information, the difference between the phase of a wave of the wobble portion when a bit takes a logical value xe2x80x9c0xe2x80x9d and the phase of a wave of the wobble portion when the bit takes a logical value xe2x80x9c1xe2x80x9d, is around 180xc2x0.
It may be in the present invention that at least one of the first sub-information and the second sub-information is an address in the track.
To also achieve the above and other objects, there is provided an optical disc which has a track for recording user data, the optical disc comprising a wobble portion waved in a radial direction of the optical disc and a non-wobble portion that is not waved provided on the track, first sub-information and second sub-information which are data other than the user data are recorded on the track by being overlapped, by using a combination of the wobble portion and the non-wobble portion, in the first sub-information, the length of at least one of the wobble portion and the non-wobble portion is different when a bit takes a logical value xe2x80x9c0xe2x80x9d and when the bit takes a logical value xe2x80x9c1xe2x80x9d, and in the second sub-information, only when a bit takes a logical value xe2x80x9c1xe2x80x9d, a phase of a wave in the wobble portion is changed with respect to a phase of a wave in the wobble portion of the preceding bit.
It may be in the present invention that, in the first sub-information, when a bit takes one of logical values xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, the non-wobble portion exists, and when the bit takes the other of logical values xe2x80x9c0xe2x80x9d and xe2x80x9c1xe2x80x9d, the non-wobble portion does not exist.
It may be in the present invention that the length of the non-wobble portion is set to be an integer multiple of one period of a wave in the wobble portion.
It may be in the present invention that the amount of a change in the phase of a wave of the wobble portion in the second sub-information is around 180xc2x0.
It may be in the present invention that at least one of the first sub-information and the second sub-information is an address in the track.
It may be in the present invention that the lengths of the wobble portion and the non-wobble portion are set to be integer multiples of one period of a wave in the wobble portion.